Spark-gap structure



Sept. 23, 1924. 1,509,497

J. SLEPIAN SPARK GAP STRUCTURE Filed Oct. 2, 1922 Joseph Slepian.

JOSEPH SLEIPIAN, or swIssvALE, PENN Patented Sept. 23, 1924.

UNITED STATES PATENT OFFICE.

SYLV'ANIA ASSIGNOR TO WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

SPARK-GAP STRUCTURE.

Application filed October 2, 1922. Serial No. 591,798.

7 '0 all whom it may concern.

Be it known that I, JOSEPH 'SLEPIAN, a citizen of the United States, and a resident of Swissvale, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Spark- Gap Structures, of which the following is a specification.

This invention relates to spark gaps, more particularly to spark. gaps which break down at voltages of 350 to 500 volts.

In practising my invention, I provide a pair of plane or flat plates or disks of highresistance material and place between the same a thin spacer or washer of suitable insulating material, such as mica, 3 to 5 mils in thickness.

It is well known that such insulating spacers placed between conducting electrodes will break down over their edges at 350 to 450 volts. This is probably due to the high dielectric constant of the mica and the leakage over the short 5-mil edge.

When metallic or low-resistance plates are used, the breakdown which occurs at the edge of the mica is followed by a discharge concentrated at that point. This dis charge causes the mica to be charred, or otherwise disintegrated, and may cause the metal to fuse together at that point. For this reason, such a gap using low-resistance or metallic plates has not proven satisfactor li y using plates of high specific resistance, the discharge which starts next to the mica surface is limited in intensity by the resistivity of the material so that the energy of the discharge is not all turned loose next to the mica but is distributed over the whole face of the plate, and the discharge takes and maintains the form of a glow dis-, charge. Thus, the mica edge is not affected by the discharge and such a gap may be used over and over again without any deterioration.

This gap is particularly useful in application to the so-called disk-pile lightning arrester, such as I have described in my copending applications, Serial No. 535,810, filed Feb.,11, 1922, for lightning arresters and Serial No. 536,910, filed Feb. 16, 1922, for disk structure.

The outstanding characteristic of lightning arresters of the type specified is that the gaps individually break down in the neighborhood of 350 volts and that the discharge is interrupted at a voltage but slightly less than the breakdown voltage, as set forth in my first-mentioned application. This operation has been provided for in my second-mentioned application by a ribbed-plate structure. The ribs are difiicult to form and are likely to be distorted during formation. Furthermore, the manufacture of plates having such ribs results in a considerable amount of breakage and imperfect plates. It is clear that the gap, which is the subject of this invention, offers many advantages over the rib construction hitherto used in the disk-pile lightning arrester.

\Vhen incorporated in a complete lightning arrester of the disk-pile type, including a series gap, difliculty often arises in that the mica spacers have such high resistance that all the line voltage is not concentrated upon the series gap, although it is desirable that the setting of the series gap should limit the line voltage.

To overcome this difiiculty, necessary to provide a leakage path through or past the gap structure so that the line voltage shall always be concentrated upon the series gap. This leakage path is most easily provided for by reducing the resistivity of the mica spacers. This is most readily done by giving the mica spacers a thin coating of india ink.

\Vith the leakage thus provided, the series gap will breakdown and the arrester will discharge when the line voltage reaches the value for. which the series gap is set.

it is merely In the accompanying drawings constituting a part hereof and in which like reference characters designate like parts,

Fig. 1 is an elevational view showing a gap consisting of two plates of high-resistance material and an insulating spacer therebetween, in accordance with my invention.

Fig. 2 is a vertical cross-sectional View of a lightning arrcster made in accordance with my invention, some parts being shown in elevation.

Fig. 3 is an enlarged plan view of one of the plates, showing spacers in position thereon, and v Fig. 4 is a view similarto Fig. 3 but illustrating a slight modification of the invention.

of plates or disks 9 of high-resistance ma:

terial, generally consisting of a suitably formed mixture of kaolin, carborundum and graphite, as described in my copendmg applications above referred to.

Interposed between the adjacent plates 9 are washers or spacers 10 of mica or other insulating material, preferably having some.

leakage. The mica washers are of such diameter that they touch'the Walls of cylinder 1, whereas the plates 9 are of slightly smaller diameter and. are spaced a short distance from said walls. The mica spacers or washers are preferably about 3 to 5 mils thick, having a coating of india ink.

A metal plate-11 is placed on the uppermost plate 9 and an insulating ring 12 is placed thereupon'to support a member .13 of metal having a depending convexly curved portion 14 to provide a series are gap between it and the metal plate-11. A spring 15 is placed on member 13, and a cover is secured in position over the assembled structure. The cover comprises an annular metal member 16 provided with exterior screwthreads 17 and secured to cylinder 1 by means of a suitable cement 18, The cover also comprises a metal cap 20 having internal screw threads to engage the threads 17. IVashers 19 are located between the cap 20 and the top of the cylinder 1 and a terminal screw 21 secures a conductor 22.10 the top of the cap.

A screw-threaded member 23 is screwed into depending flange 4 and has a bracket 24 firmly secured thereto by means of screw 25. A depending portion '26 on bracket 24 is provided with a series of openings 27 to enable the lightning arrester to be fixed in position on the cross-arm of a pole or in any. other suitable position.

Although I have shown the use of annular mica washers as spacers between adjacentplates, it is not necessary that the spacers be of such form. For instance, in Fig. 3 I have illustrated a series of-uniformly spaced mica disks 28 and in Fig. 4 strips 29, the ends of which project'beyond the edges of the plates 9. Said embodiments of my invention are equally'effective in providing the desired breakdown voltage, although the form illustrated in Fig. 1 has the additional advantage of preventing accidental arcing alongthe outer edges of the plates the mica used and the spacers may be of any desired form; A poor insulating material having sufficient leakage may be used in place of the coated mica.- Although the plates are spaced apart about 3 mils, it is obvious that any other suitable spacing to give the desired results may be utilized. These and various other changes in the details of my invention may be made within the scope thereof.

Although I have described a preferred structure as comprising a plurality of plates of relatively high-resistance material, I desire it to be understood that one of the plates for each gap or one of the plates foreach of a plurality of gaps but less than the whole number may be of relatively low resistance, such as metal, if desired. I desire, therefore, that my invention shall be understood as comprising these modifications and such others as may ensure the results hereinbefore specified.

I claim as my invention:

1. A gap structure for lightning arresters comprising a plurality of plates spaced apart and means therebetween to cause the gaps between adjacent plates to break down at about 350 to 450 volts, at least some of said plates beingof relatively high resistance material. I

2. A gapstructure for lightning arresters comprising a plurality of plates spaced apart and means therebetween to cause the gaps between adjacent plates to break down at about 350 to 450 volts, at least one of the plates of each gap being of relatively high resistance material.

3. A gap structure for lightning arresters comprising a plurality of plates spaced apart and spacers therebetween, the average distance between the plates being approximately3 to 5 mils, at 'least one of the plates of each gap being of relatively high resistance material.

at. A gap structure for lightning arresters comprising a pair of plates and a spacer of about 5 mils thickness therebetween, at least one of said plates being of relatively h gh resistance material.

5. A lightning arrester comprising a plurality of plates of relatively high resistance material spaced apart and means therebctween to cause the gaps between adjacent plates to breakdown at about 350 to 450 volts.

6. A lightning arrester comprising a plurality of plates of relatively high resistance material spaced lating material therebetween to cause the gaps between adjacent plates to break down at about 350 to 450 volts. I

7. A lightning arrester comprising a plurality of plates of relatively high resistance material and spacers therebetween, the thickness of the spacers being such that the breakdown voltage does not exceed about 450 volts.

8. A lightning arrester comprising a plurality of plates of relatively high resistance material and spacers therebetween, the thickness thereof being 3 to 5 mils.

9. A lightning arrester comprising an enclosing casing, tively high resistance material and insulating washers therebetween, said washers extending beyond the edges of said plates and spacing the same from the walls of said casing, the thickness of said washers being such that the breakdown voltage does not exceed about 450 volts.

10. A lightning arrester com rising a plurality of plates of relatively high resistance material, spacers therebetween,'and conducting material on said spacers, the thickness of said spacers being such that the breakdown voltage does not exceed about 450 volts.

11. A lightning arrester comprising a plurality of plates of relatively hlgh resistance material, thin spacers therebetween, and a coating of india ink on said spacers.

12. A lightning arrester comprislng a plurality of plates or relatively high resistance material, mica spacers therebetween, the thickness thereof being about 3 to 5 mils, and conducting material on said spacers.

13. A lightning arrester com rising a plurality of plates of relatively high resistance material, mica spacers therebetween, the thickness thereof being 3 to 5 mils, and a coating of india ink on said spacers.

14. A lightning arrester comprising a plurality of plates of relatively high resistance material, spacers therebetween, the thickness thereof being 3 to 5 mils, said spacers extending beyond the edges of said plates and a coating of india ink thereon.

15. A lightning arrester comprising :1 cylinder of insulating material, a plurality of plates of relatively high resistance material and thin spacers therebetween, said spacers extending beyond the edges of said lates and making contact with the walls 0 said cylinder.

16. A lightning arrester comprising a series are gap, a plurality of lates of relatively high resistance materiai: thin spacers therebetween, and conducting material on apart and spacers of insu-' a plurality of plates of relasaid spacers, the thinness of said spacers being such as to insure a -glow discharge.

17. A lightning arrester comprising a series are gap, a plurality of plates of relatively high resistance material, thin spacers therebetween, providing a plurality of serially connected glow-discharge gaps, and a coating of india ink on said spacers, the resistance and spacing of said plates being such that the breakdown voltage does not materially exceed the voltage at which the discharge is interruptedin said glow-discharge gaps.

18. A lightning arrester comprising a series gap, a plurality of plates of relatively high resistance material, mica s acers therebetween, the thickness thereof eing 3 to 5 mils, and conducting material on said spacers.

19. A lightning arrester comprising a lurality of spaced bodies of relatively highresistance material and means'to cause the gaps between adjacent bodies to break down .at approximately the voltage necessary to maintain the discharge.

20. A lightning arrester com rality of spaced bodies of re atively h1 hresistance material and means for initiating a discharge between the bodies at a voltage slightly above that necessary to maintain the discharge and then spreading the discharge over the surfaces of the bodies.

21. A lightning arrester comprising a plurality of spaced bodies of relatively highresistance material and means therebetween to cause the gaps between adjacent bodies to break down at approximately the voltage necessary to maintain the dischar e.

22. A lightning arrester comprising a lurality of spaced bodies of relativel hlghresistance material and-means there etween for initiating a discharge between the bodies at a voltage slightly above that necessar to maintain the discharge and then spre ing the discharge over the surfaces of the bodies.

23. A lightning arrester comprising a pair of spaced bodies, at least one of which is of relatively high-resistance material, and means to cause the gap between said bodies to break down at approximately the voltage necessary to maintain the discharge.

24. A lightning arrester comprising a pair of spaced bodies, at least one of which is of relatively high-resistance material, and means therebetween to cause the gap between said bodies to break down at approximately the voltage necessary to maintain the discharge.

In testimony whereof, I have hereunto subscribed my name this 13th day of September 1922.

rising a lu- JOSEPH SLEPIAN. 

